Chapter 139:21Chanukah

21. Throughout the eight days of Chanukah, the prayer "Al HaNissim" (1)
should be added to the "Shemoneh Esreh" (in the blessing of thanksgiving
("hoda'ah") beginning with the word "Modim"). [The following rules apply]
if one forgot to recite it: If one remembers before mentioning G-d's name
in the blessing "HaTov Shimchoh..," one should say "Al HaNissim" [and then
complete the blessing] (2). However, if one remembered [one's exclusion of
"Al HaNissim"] only after one had already said G-d's Name, one should
conclude the blessing (ending with "Hatov Shimchoh") without going back [to
say "Al HaNissim"] (3). ([The laws regarding the recitation of Al hanissim]
in "Birchas HaMazon" ("Grace after Meals") are discussed in Chapter 44, Law
16.)

FOOTNOTES:

(1) "Al HaNissim" is a prayer which thanks G-d for the miracles he
performed for our ancestors.

(2) This is true even if he had already said the words "Baruch Ata..."

(3) In that case, one should, however, recite "Al HaNissim" in the form of
a request, after the passage "E-lokai n'tzor" before the final "Yih'yu
l'rotzon.." at the end of Shemoneh Esrei; that is, one should say:
"Horachaman Hu Ya'aseh Lanu Nissim..." ("May the Merciful One perform
miracles and wonders for us, like He performed for our ancestors") (Mishnah
Berurah 682:4).